The invention relates to a method for operating a measuring apparatus for determining the flow rate of flowable media through a measuring section, wherein the measuring apparatus operates with an ultrasonic phase difference method and has as sensors at least two ultrasonic transceivers, which are arranged at a distance from one another to expose the measuring section to sonic waves in and against the direction of flow and to receive signals. Furthermore the invention also relates to a measuring device to determine the flow rate of flowable media through a measuring section, for example in the above-mentioned method.
The determination of the flow rate of flowable or fluid media can occur via different methods, one of which represents measuring via ultrasound, known per se. Using the known ultrasonic measurement method, e.g., the sing around method (sequential pulse frequency method) continuous flow rates can be measured well. However, here a relatively long measuring period is necessary, so that the use of such methods is not recommended for rapidly changing flow rates. Direct time measurements with transit time techniques are rather unsuitable under such conditions, because a value for the flow rate can only be calculated from the spread of the sound delay including a couple of measurement cycles.
In addition to the known methods already mentioned, so-called ultrasonic phase difference methods to determine the flow rate of the medium through the measuring section are also known from CH 604 133 or DE 37 34 635 A1, for example. The methods suggested here have the disadvantage, though, that one the one hand the measurements are disturbed by a multitude of analog components, the receiver signals can mutually influence each other, and the direction of flow is not known, on the other hand, a high circuit expenses must be invested to shift the phase of measuring signals and a subsequent synchronization.